JPH0450663B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a photoresist developing device used for manufacturing master discs of optical discs used in optical recording and reproducing devices such as video discs.

[Background of the invention]

An optical disk has a transparent disc-shaped substrate with one helical track that can be divided into a number of concentric tracks or a number of quasi-concentric tracks, and these tracks are formed by discontinuous pits or protrusions. It consists of When reproducing an optical disk, a laser beam is irradiated onto an optical pattern consisting of pits or protrusions on the surface of the disk while rotating the recording medium, and the laser beam is modulated by the optical pattern. The optical pattern is converted into an electrical signal and the information corresponding to the optical pattern is reproduced. The master disc used to manufacture this disc is a polished glass substrate with a positive photoresist film on the surface, and this photoresist film is continuously irradiated with laser light according to the information to be recorded on the master disc. The photoresist film is exposed discontinuously according to the track, and the exposed parts of the photoresist film are dissolved and removed by a developer.
In its wake, a row of concave portions called pits are formed concentrically or spirally. Optical discs are mass-produced from master discs with such pits by manufacturing molds for reproduction (stampers) and using methods such as injection molding, in the same way as conventional audio discs with continuous sound grooves. .

The dimensions of the pits formed in the above development process are closely related to the performance during disk playback.
Therefore, the developing process must be controlled so that the bit dimensions (depth and width) are within a predetermined range. Therefore, in the past, a method has been adopted in which the duration of the chemical reaction in which the exposed portion of the photoresist is dissolved in the developer, that is, the development time, is adjusted based on intuition gained from experience. However, the rate of progress of such chemical reactions varies depending on conditions such as the degree of exposure, developer concentration, and temperature.
With the conventional method of adjusting development time by intuition without monitoring the depth or width of the pits that are being formed during development, the size of the pits cannot be known until the development process is complete. Therefore, variations occur in the depth or width of the pits in the developed master. In order to improve this problem, as shown in FIG. 1, while rotating the master 1, the developer 4 is sprayed onto the photoresist film surface from the nozzle 3 to advance the development, and the developer 4 is sprayed from the nozzle. A photoresist developing method configured to monitor the dimensions of pits during development at a position using an optical method using diffraction development of laser light, etc., and to stop the development process when the pit dimensions reach a predetermined value. is proposed. In the example shown in FIG. 1, the first-order diffracted light of the laser beam generated by the pits of the master changes in accordance with the depth and width of the pits, and when the intensity reaches a predetermined level, development is stopped. However, it is not easy to stably detect the first-order diffracted light during development. In other words, the developer is sequentially supplied to the master surface, and since the master is rotating, the liquid level on the master surface is constantly fluctuating.
As shown in FIG. 2, the first-order diffraction light changes greatly due to fluctuations, and the original intensity of the first-order diffraction (dotted line in FIG. 2) cannot be detected accurately. In order to improve this, it is conceivable to pass the first-order diffraction optical signal through a low-pass filter with a low cutoff frequency to remove noise. However, achieving sufficient stability with this method impairs the ability to follow changes in the first-order diffracted light, making it difficult to make optimal decisions even by monitoring the first-order diffracted light. . As a result, it is not possible to control the pit depth and width of the master after development with sufficient accuracy.

As described above, in the conventional technology, even if an optical monitoring system is employed, sufficient results cannot be obtained, and the pit size of the master disk after development varies.

[Purpose of the invention]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a photoresist developing apparatus which improves the above-mentioned drawbacks of the prior art and allows optically stable monitoring of pit dimensions during development.

[Summary of the invention]

The present invention is designed to suppress fluctuations in the developer level on the rotating master surface during photoresist development processing, and to allow monitor light to stably pass through the master surface. This photoresist developing device is characterized in that the supply is made into a laminar flow, a region is provided in which the developer in contact with the surface of the master flows in a laminar flow in the direction of rotation of the master, and this region is irradiated with monitor light.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 3 shows a first embodiment of the invention. A master disk 1 on which a photoresist film has been exposed is rotating horizontally at about 300 rpm, and a developer 4 is supplied to the surface of the master disk in a laminar flow as shown in FIG. 3 from a circular nozzle 3 having a diameter of 6 mm. At this time, the developer spreads on the master surface as shown in FIG. 3 and flows laminarly for a while along the direction of rotation of the master, and the level of the developer is smooth and stable in this region. Therefore, by irradiating this position with the He-Ne laser beam 55 from the back side of the master, the first-order diffracted light diffracted by the row of pits formed when the photoresist film on the surface of the master is developed has a stable intensity and direction. The signal detected by the photodiode 20 has little noise and is stable, as shown in FIG. Therefore, it is possible to accurately determine whether the intensity of the first-order diffracted light has reached a predetermined value, and it is possible to appropriately stop the development process. That is, the pit dimensions can be finely adjusted, and the present invention has a great effect on improving the precision of the pit dimensions of the master.

In the first embodiment described above, one circular nozzle was used, but when developing a large master disk (360 mm in diameter) used for manufacturing optical disks of 30 cm in diameter, one nozzle does not require enough developer solution. Because it is not easy to supply uniformly, as shown in Figure 5, the width is approximately
By using a nozzle with a slit outlet of 0.5 mm and length of 100 mm to supply the developer in a long and narrow laminar flow, the entire pit row of the master can be uniformly brought into contact with the developer. In this case, as in the first embodiment, if the laser beam 55 is irradiated to the position where the developer flows in a laminar flow near the nozzle and the first-order diffracted light is monitored, a stable signal can be obtained as described above. Therefore, the development process can be appropriately stopped. Therefore, in this case as well, the same effects as in the first embodiment can be obtained.

In addition, as a third embodiment, as shown in FIG. 6, the developer supply arm 7 having a plurality of nozzles allows the developer to flow in a laminar flow to each nozzle, and in the vicinity of any nozzle, Similarly, by irradiating with laser light, stable detection of first-order diffracted light becomes possible. At this time, by swinging the developer supply arm 7, it is possible to uniformly supply the developer to the entire pit row even on a large master, and this greatly reduces the variation in pit dimensions caused by variations in development speed within the master. It can be improved. This embodiment has the advantage that the amount of developer discharged can be reduced to 1/3 or less compared to the second embodiment due to the difference in nozzle shape. FIG. 7 schematically shows the developing device according to this embodiment. The master 1, which has undergone the prescribed exposure process, is placed on the turntable in the development chamber 45, rotated at approximately 300 rpm, and the developer supply arm 7, which has eight nozzles (diameter approximately 2 mm), is swung along the surface of the master. While moving, approximately 1 developer per minute is supplied from each nozzle in a laminar flow. Next, He−
Ne laser light is irradiated from the back side of the master disc, and the laser light irradiation position is set to fall into one of the laminar flows of developer created for each nozzle. At this time, even if the arm swings and the flow of the developer changes, the laser irradiation position must always remain in a stable laminar flow state. When using the 8-nozzle arm of this example, the swing angle of the arm can be made considerably smaller (30 degrees or less) compared to a small number of nozzles, so fluctuations in the flow of developer due to arm swing are small, and laser irradiation is reduced. It is easy to set the direction of the arm swing so that the developer always flows in a laminar flow at the position. In this state, development progresses,
When pits are formed on the photoresist film on the surface of the master, the laser beam is diffracted by the rows of pits arranged at a pitch of 1 to 2 μm. This first-order diffracted light is detected by the photodiode 20, and when it reaches a predetermined value with respect to the intensity of the incident light 55, the control circuit automatically operates to stop the supply of the developer and replace the developer with water. Flow it through the nozzle to stop development. At this time as well, the flow rate of water from the nozzle is set at about 1/min so that the water flows in a laminar flow. Furthermore, a nozzle exclusively for water is installed at the tip of the arm to completely remove any developer attached to the inner periphery of the master. Finally, the water is turned off and the master is rotated at high speed (approximately 1000 rpm) to remove water and dry it. As described above, according to this embodiment, it is possible to stably detect the 1st time diffracted light, and to appropriately stop development. Therefore, it is clear that the present invention has a great effect on improving the dimensional accuracy of the pits of the master. Furthermore, in the present invention, since the developer is supplied in a laminar flow, there is no scattering of the developer compared to the conventional spray method, and furthermore, the developer that has been shaken off from the master is returned to the surface of the master. By partitioning the developing chamber with an adhesion prevention plate 40 shown in FIG. 7 to prevent foreign matter from coming back, it is possible to completely prevent foreign matter from adhering to the master surface during the development process. Therefore, the present invention significantly reduces the number of defects on master discs, and has a great effect on reducing dropouts of optical discs.

In the above embodiments, the case where laser diffraction light is monitored is explained as an example, but the present invention has similar effects even when an optical monitor using light from a tungsten lamp, xenon lamp, etc. is used instead of laser light. .

Furthermore, although the present invention has been explained using an optical disk as an example, the present invention can also be applied when a pin development method using an optical monitor is used in the development of photoresist films used in semiconductors, etc., and the above-mentioned effects can be obtained. I can do it.

〔Effect of the invention〕

According to the present invention, the pit size of a master disc such as an optical disk can be stably adjusted using an optical monitor during the development process, which has a great effect on improving the accuracy of the pit size of the master disc.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing a conventional developing method, Fig. 2 is a relationship diagram between the development time and the intensity of the first-order diffracted light processed by the conventional developing method, and Fig. 3 shows the first embodiment of the present invention. A schematic diagram, FIG. 4 is a relationship diagram between the development time and the intensity of the first-order diffracted light in the present invention, FIG. 5 is a schematic diagram showing the second embodiment of the present invention, and FIG. 6 is a diagram showing the third embodiment of the present invention. A schematic diagram showing an example, and FIG. 7 is a schematic diagram showing a developing device of the present invention. 1...Master disc, 2...Turntable, 3...Developer nozzle, 4...Developer, 5...Laser, 7...
... Arm, 20... Photo diode, 40... Anti-adhesion plate, 45... Chamber.

Claims (1)

[Claims] 1. While rotating a substrate having a photoresist film that has been exposed to light on its surface, the photoresist film is developed by bringing a developer into contact with the surface, and the progress of the development is monitored by an optical method, and based on the monitored value. In the developing device that stops the development process, the flow of the developer from the developer nozzle to the substrate surface is made into a laminar flow, and an area is provided in which the developer in contact with the substrate surface flows in a laminar flow in the direction of rotation of the substrate. A photoresist developing device characterized in that the irradiation position of the monitor light is set in a region.